Overflow history upstream of River Thames, Buscot Weir

The spot's forecast · For event organisers

This page lists the monitored storm overflows upstream of this spot and how often each spilled in each year. It is not a water test, and it does not say whether the water is fit to swim in. It does not include farm runoff, misconnected drains, treated sewage effluent, wildlife or overflows without a monitor. A year's count depends on how long the monitor worked, shown as monitor uptime.

Each year, all overflows upstream

Year	Overflows with a return	Spills	Spill hours	Spill hours, weighted by reach
2021	18	639	8,892	92
2022	17	450	5,572	56
2023	22	1,414	23,022	231
2024	22	1,719	28,910	323
2025	22	816	12,891	135

Reach is the share of a spill's bacteria SwimSignal's model expects to arrive here, after die-off on the way and dilution by the river. Weighting by it counts an hour of spilling just upstream for far more than one 40 km away. Spills are counted by the Environment Agency's 12/24 method: any discharge in the first 12 hours counts as one spill, then one more for each 24 hours with any discharge. How reach is worked out.

The overflows, by reach

All 22, the one whose spills matter most here first. Hours away is how long sewage takes to arrive at the model's river speed.

Overflow and id	Company	km upstream	Hours away	Reach	Spills 2023	Spills 2024	Spills 2025	Spill hours 2025	Monitor uptime 2025
Fairford sewage works overflow Fairford STW · TWL00178	Thames Water	12.0	7	3%	162	202	107	2,235	100%
Lechlade sewage works overflow Lechlade STW · TWL00263	Thames Water	2.8	2	2%	45	128	11	161	100%
Shrivenham sewage works overflow Shrivenham STW · TWL00368	Thames Water	20.7	12	2%	81	125	56	946	100%
Highworth sewage works overflow Highworth STW · TWL00227	Thames Water	12.2	7	1%	60	66	27	340	100%
Kilda Road (Highworth) pumping station overflow Kilda Road (Highworth) SPS · TWL00249	Thames Water	12.6	7	1%	0	0	0	0	96%
Hannington TWL00130	Thames Water	13.4	7	1%	21	21	8	14	100%
Kempsford sewage works overflow Kempsford STW · TWL00246	Thames Water	9.3	5	1%	8	8	0	0	100%
Swindon sewage works overflow Swindon STW · TWL00402	Thames Water	29.9	17	1%	62	47	23	288	100%
Wanborough sewage works overflow Wanborough STW · TWL00422	Thames Water	27.1	15	1%	102	150	68	822	100%
Highworth Eastrop (GWA site) storm overflow Highworth Eastrop CSO (GWA site) · TWL00226	Thames Water	13.9	8	1%	32	29	9	12	90%
Blunsdon sewage works overflow Blunsdon STW · TWL00046	Thames Water	15.7	9	1%	19	13	9	54	98%
Stanton Fitzwarren pumping station overflow Stanton Fitzwarren SPS · TWL00723	Thames Water	17.6	10	1%	11	20	0	0	100%
Ampney St Peter sewage works overflow Ampney St Peter STW · TWL00010	Thames Water	28.6	16	0%	130	147	68	1,436	93%
Cricklade sewage works overflow Cricklade STW · TWL00119	Thames Water	20.5	11	0%	114	107	59	641	100%
Sevenhampton sewage works overflow Sevenhampton STW · TWL00362	Thames Water	21.0	12	0%	103	135	99	2,055	100%
Hatchetts (Cricklade) pumping station overflow Hatchetts (Cricklade) SPS · TWL00600	Thames Water	20.5	11	0%	31	56	33	378	100%
Cirencester sewage works overflow Cirencester STW · TWL00102	Thames Water	29.7	16	<1%	165	236	125	2,067	100%
Minety Station Road WXW01061	Wessex Water	31.8	18	<1%	80	45	22	171	100%
Purton sewage works overflow Purton STW · TWL00337	Thames Water	26.8	15	<1%	41	53	27	322	100%
Hankerton Hankerton Bridge WXW00500	Wessex Water	38.5	21	<1%	78	65	34	549	100%
Chisledon storm tank overflow Chisledon storm tanks · TWL00790	Thames Water	34.0	19	<1%	23	18	2	8	100%
Upper Minety Flisteridge WXW00433	Wessex Water	39.1	22	<1%	46	48	29	393	95%

A dash: no annual return for that overflow in that year.

Sources and credits

Storm overflow annual returns: © Environment Agency copyright and/or database right 2025, Open Government Licence v3.0. Overflow positions: the water companies via the National Storm Overflow Hub, CC BY 4.0. River network: contains OS data © Crown copyright and database right 2026 (OS Open Rivers). Traced and weighted by SwimSignal (swimsignal.co.uk), whose method is at swimsignal.co.uk/methods.html. All credits and licences.